Researchers have developed a hand-held breath-testing device designed to measure acetone levels in exhaled air, offering a portable way to track fat metabolism during dieting or exercise. The technology detects acetone—a physiological by-product produced when the human body burns fat rather than carbohydrates like sugar—with an accuracy nearly matching that of laboratory-grade mass spectrometers.
Unlike clinical analyzers or bulky stationary equipment, the newly validated instrument functions similarly to a law enforcement breathalyzer. Operated alongside a smartphone application, the system allows individuals to monitor shifts in their metabolism independently, removing the immediate need for professional support or frequent blood draws.
“When it comes to diets, there’s no rule of thumb that works for everybody. Ideally, people should self-monitor to see how their own metabolism responds,” explains Andreas Güntner, professor of molecular sensing at ETH Zurich’s mechanical and process engineering department.
“Methods are also needed that can be carried out independently and that produce reliable results, similar to blood glucose measurements for diabetics.”
Validation Study and Sensor Technology
The measuring device was developed by Güntner’s research group at ETH Zurich in collaboration with Alivion, an ETH spin-off company, with reliability tested alongside the University Hospital Zurich. To verify its accuracy, the research team conducted a validation study involving 12 adult participants.
During the study, scientists recorded 312 separate breath readings using the hand-held tool. They compared these results directly against traditional blood test outcomes and measurements captured by a high-precision mass spectrometer, which serves as the analytical gold standard for gas detection. Testing took place across various metabolic scenarios, including light and intensive physical activity as well as distinct dietary regimens. Results showed that readings from the portable device were practically identical to lab measurements, maintaining reliability over a period of months.
The underlying sensor technology builds upon more than a decade of development at ETH Zurich, first publicly demonstrated in 2017. At that time, researchers established that their gas sensors could detect a single acetone molecule among 100 million other air molecules.
Standard acetone breath-testers currently available on the market often suffer from limited reproducibility, capturing only major metabolic shifts. Furthermore, these devices can respond to other components of exhaled air, for example if test subjects ate or drank something beforehand. To solve this, the research team engineered an integrated filter designed to block interfering molecules, alongside a smartphone app that guides users through the exhalation process in real time.
“The device measures the volume of exhaled air and only takes a sample that comes from deep in the lungs after a certain time,” says lead author Simone Hersberger, adding: “otherwise, every reading would be slightly different.” Calibrating the units to each patient’s specific lung volume makes this selective sampling possible.
“We were able to demonstrate that our device can detect slight differences in fat metabolism accurately and reliably,” says Hersberger, an ETH doctoral student.
Potential Applications in Medical Therapy and Sports
Following the validation study, published in the journal Device, the researchers are exploring several clinical and lifestyle applications. Future studies aim to determine whether the breathalyzer can help personalize treatments for metabolic disorders.
In cooperation with the University Children’s Hospital Zurich, investigators are examining whether the hand-held tool can assist children with epilepsy in closely tracking ketogenic diets. Additional prospective uses include monitoring medical nutrition plans, optimizing GLP-1 therapies with weight loss jabs, and supporting amateur athletic training.
Alivion AG has commercialized the technology under the trade name Nutrion. The units are currently deployed in medical facilities and international research studies, while the company seeks strategic investors and industry partners to scale manufacturing and expand its market reach.
“This example shows how the results of basic research can be put into practice and ultimately help society,” says Güntner.
The research project received financial backing from Innosuisse, the Vontobel Foundation, and the Accentus Foundation.
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